usbnet: make usbnet_get_link() fall back to ethtool_op_get_link()

Make usbnet_get_link() fall back to ethtool_op_get_link() instead of
defaulting to 1.  
     
This makes usbnet_get_link return valid results without the need for a
driver specific check_connect or mii ops as long as the driver calls
netif_carrier_{on,off}() as appropriate.  cdc_ether is an example of
such a driver.
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/usbnet.c

@@ -723,8 +723,8 @@ u32 usbnet_get_link (struct net_device *net)
 	if (dev->mii.mdio_read)
 		return mii_link_ok(&dev->mii);
 
-	/* Otherwise, say we're up (to avoid breaking scripts) */
-	return 1;
+	/* Otherwise, dtrt for drivers calling netif_carrier_{on,off} */
+	return ethtool_op_get_link(net);
 }
 EXPORT_SYMBOL_GPL(usbnet_get_link);